Interoperability for bluetooth/IEEE 802.11

ABSTRACT

The key of the invention is to introduce an interoperability device in a communication system which integrates an IEEE 802.11 transceiver and a Bluetooth transceiver. The device prevents that one transceiver is transmitting while the other is receiving, which would cause interference at the receiving transceiver. In addition, the device preferably prevents that both systems are transmitting at the same time to avoid interference at the receiving device(s). Optionally the device prohibits simultaneous reception of both transceivers. In that way the radio receiver can be shared between the devices, allowing a cheaper and smaller hardware design.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority of European Patent ApplicationNo. 00300397.7, which was filed on Jan. 20, 2000.

FIELD OF THE INVENTION

[0002] The present invention relates to both Bluetooth and IEEE 802.11radio communication systems.

DESCRIPTION OF THE RELATED ART

[0003] IEEE 802.11 is a standard for wireless systems that operate inthe 2.4-2.5 GHz ISM (industrial, scientific and medical) band. This ISMband is available world-wide and allows unlicensed operation for spreadspectrum systems. For both the US and Europe, the 2,400-2,483.5 MHz bandhas been allocated, while for some other countries, such as Japan,another part of the 2.4-2.5 GHz ISM band has been assigned. The 802.11standard focuses on the MAC (medium access control) protocol and PHY(physical layer) protocol for access point (AP) based networks andad-hoc networks.

[0004] In access point based networks, the stations within a group orcell can communicate only directly to the access point. This accesspoint forwards messages to the destination station within the same cellor through a wired distribution system to another access point, fromwhich such messages arrive finally at the destination station. In ad-hocnetworks, the stations operate on a peer-to-peer level and there is noaccess point or (wired) distribution system.

[0005] The 802.11 standard supports: DSSS (direct sequence spreadspectrum) with differential encoded BPSK and QPSK; FHSS (frequencyhopping spread spectrum) with GFSK (Gaussian FSK); and infrared with PPM(pulse position modulation). These three physical layer protocols (DSSS,FHSS and infrared) all provide bit rates of 2 and 1 Mbit/s. The 802.11standard further includes extensions 11 a and 11 b. Extension 11 b isfor a high rate CCK (Complementary Code Keying) physical layer protocol,providing bit rates 11 and 5.5 Mbit/s as well as the basic DSSS bitrates of 2 and 1 Mbit/s within the same 2.4-2.5 GHz ISM band. Extension11 a is for a high bit rate OFDM (Orthogonal Frequency DivisionMultiplexing) physical layer protocol standard providing bit rates inthe range of 6 to 54 Mbit/s in the 5 GHz band.

[0006] The 802.11 basic medium access behavior allows interoperabilitybetween compatible physical layer protocols through the use of theCSMA/CA (carrier sense multiple access with a collision avoidance)protocol and a random back-off time following a busy medium condition.In addition all directed traffic uses immediate positive acknowledgement(ACK frame), where a retransmission is scheduled by the sender if nopositive acknowledgement is received. The 802.11 CSMA/CA protocol isdesigned to reduce the collision probability between multiple stationsaccessing the medium at the point in time where collisions are mostlikely occur. The highest probability of a collision occurs just afterthe medium becomes free, following a busy medium. This is becausemultiple stations would have been waiting for the medium to becomeavailable again. Therefore, a random back-off arrangement is used toresolve medium contention conflicts. In addition, the 802.11 MACdefines: special functional behavior for fragmentation of packets;medium reservation via RTS/CTS (request-to-send/clear-to-send) pollinginteraction; and point co-ordination (for time-bounded services).

[0007] The IEEE 802.11 MAC also defines Beacon frames, sent at a regularinterval by an AP to allow STAs to monitor the presence of the AP. IEEE802.11 also defines a set of management frames including Probe Requestframes which are sent by an STA, and are followed by Probe Responseframes sent by the AP. Probe Request frames allow an STA to activelyscan whether there is an AP operating on a certain channel frequency,and for the AP to show to the STA what parameter settings this AP isusing.

[0008] Bluetooth technology allows for the replacement of the manyproprietary cables that connect one device to another with one universalshort-range radio link. For instance, Bluetooth radio technology builtinto both a cellular telephone and a laptop would replace the cumbersomecable used today to connect a laptop to a cellular telephone. Printers,personal digital assistant's (PDA's), desktops, computers, fax machines,keyboards, joysticks and virtually any other digital device can be partof the Bluetooth system. But beyond un-tethering devices by replacingthe cables, Bluetooth radio technology provides a universal bridge toexisting data networks, a peripheral interface, and a mechanism to formsmall private ad-hoc groupings of connected devices away from fixednetwork infrastructures.

[0009] Designed to operate in a noisy radio frequency environment, theBluetooth radio system uses a fast acknowledgement and frequency hoppingscheme to make the link robust. Bluetooth radio modules avoidinterference from other signals by hopping to a new frequency aftertransmitting or receiving a packet. Compared with other systemsoperating in the same frequency band, the Bluetooth radio systemtypically hops faster and uses shorter packets. This makes the Bluetoothradio system more robust than other systems. Short packets and fasthopping also limit the impact of domestic and professional microwaveovens. Use of Forward Error Correction (FEC) limits the impact of randomnoise on long-distance links. The encoding is optimised for anuncoordinated environment. Bluetooth radios operate in the unlicensedISM band at 2.4 GHz. A frequency hop transceiver is applied to combatinterference and fading. A shaped, binary FM modulation is applied tominimise transceiver complexity. The gross data rate is 1 Mb/s.

[0010] A Time-Division Duplex scheme is used for full-duplextransmission. The Bluetooth baseband protocol is a combination ofcircuit and packet switching. Slots can be reserved for synchronouspackets. Each packet is transmitted in a different hop frequency. Apacket nominally covers a single slot, but can be extended to cover upto five slots. Bluetooth can support an asynchronous data channel, up tothree simultaneous synchronous voice channels, or a channel whichsimultaneously supports asynchronous data and synchronous voice. Eachvoice channel supports 64 kb/s synchronous (voice) link. Theasynchronous channel can support an asymmetric link of maximally 721kb/s in either direction while permitting 57.6 kb/s in the returndirection, or a 432.6 kb/s symmetric link.

[0011] The IEEE 802.11 standard is well-established and local areanetworks are already implemented based on the standard, typically inoffice environments. As Bluetooth comes into the market, it is likely tobe implemented in a domestic environment for communications within thehome, for example. Thus someone with a lap-top computer may wish toconnect to a IEEE 802.11 wireless local area network in the workplace,and connect to a device, such as a mobile telephone, using a Bluetoothinterface outside of the workplace.

[0012] A need exists for a means which can enable a single device tointerface via both an IEEE 802.11 radio system and a Bluetooth radiosystem.

SUMMARY OF THE INVENTION

[0013] According to one aspect of the present invention there isprovided a device incorporating a first radio system operating at afirst range of frequencies of operation and a second radio systemoperating at a second range of frequencies of operation, wherein atleast a part of said first and second range of frequencies overlap,wherein the device further includes a control means adapted to controlthe first and second radio systems such that such that only one or theother radio system may transmit at any one time. The first radio systemmay be a Bluetooth system and the second radio system may be an IEEE802.11 system.

[0014] The device may be additionally controlled such that when onedevice is transmitting the other device cannot receive or transmit. Thedevice may be additionally controlled such that when one device isreceiving the other device cannot receive or transmit.

[0015] The control means may comprise a switching means, the switchingmeans being adapted to switch on and off the first and second radiosystems.

[0016] The control means may comprise a multiplexing means adapted totime multiplex transmissions from the first and second radio systems.

[0017] The control means may comprise a multiplexing means adapted totime multiplex transmissions from the Bluetooth and IEEE 802.11 radiosystems, the IEEE 802.11 and Bluetooth transmissions being multiplexedinto Bluetooth time-slots.

[0018] The Bluetooth transmissions may be through a single HV2 SCO linkconnection, the IEEE 802.11 transmissions being in two time-slots inevery four. The Bluetooth transmissions may be through a single HV3 SCOlink connection, the IEEE 802.11 transmissions being in four time-slotsin every six. The Bluetooth transmissions may be through two HV3 SCOlink connections, the IEEE 802.11 transmissions being in two time-slotsin every six.

[0019] The control means may prevent transmission of IEEE 802.11 packetsduring a Bluetooth ACL packet transmission. The control means mayprevent transmission of Bluetooth ACL packets during an IEEE 802.11packet transmission.

[0020] The first and second radio systems may share a common physicallayer.

[0021] According to another aspect of the present invention there isprovided a method of incorporating a first radio system operating at afirst range of frequencies of operation and a second radio systemoperating at a second range of frequencies of operation, wherein atleast a part of said first and second range of frequencies overlap, intoa single device, wherein the first and second radio systems arecontrolled such that only one or the other radio system may transmit atany one time. The first radio system may be a Bluetooth system and thesecond radio system may be an IEEE 802.11 system.

[0022] The method may further comprise controlling the radio systemssuch that when one radio system is transmitting the other device cannotreceive or transmit.

[0023] The method may further comprise controlling the radio systemssuch that one device is receiving the other device cannot receive ortransmit.

[0024] The radio systems may be controlled by switching on and off thefirst and second radio systems.

[0025] The radio systems may be controlled by time multiplexingtransmissions from the first and second radio systems.

[0026] The method may comprise time multiplexing transmissions from theBluetooth and IEEE 802.11 radio systems, the IEEE 802.11 and Bluetoothtransmissions being multiplexed into Bluetooth time-slots.

[0027] The Bluetooth transmissions may be through a single HV2 SCO linkconnection, the IEEE 802.11 transmissions being in two time-slots inevery four. The Bluetooth transmissions may be through a single HV3 SCOlink connection, the IEEE 802.11 transmissions being in four time-slotsin every six. The Bluetooth transmissions may be through two HV3 SCOlink connections, the IEEE 802.11 transmissions being in two time-slotsin every six.

[0028] The method may further comprising preventing transmission of IEEE802.11 packets during a Bluetooth ACL packet transmission. The methodmay further comprising preventing transmission of Bluetooth ACL packetsduring an IEEE 802.11 packet transmission.

[0029] The first and second radio systems may share a common physicallayer.

[0030] Therefore if both an IEEE 802.11 radio transceiver and aBluetooth radio transceiver reside in a single device (for instance in alaptop computer) they can transmit and receive in the same radiofrequency simultaneously, even though both communication standards makeuse of the same 85 MHz wide ISM band, at around 2.4 GHz. This isachieved by a Bluetooth device in a computer being prevented fromtransmitting data whilst an 802.11 device is attempting to receive dataand vice versa.

[0031] Even if the RF frequency that the receiving device is tuned to isdifferent, but still in the same band that the transmitting device isusing, the emitted power will jam the receiver, rendering it unable toreceive the intended signal.

[0032] The invention solves this problem by introducing aninteroperability device, that is connected both to the medium accesscontroller of the IEEE 802.11 device and to the baseband controller ofthe Bluetooth device.

[0033] The invention also proposes an alternative solution, called dualmode operation, where the IEEE 802.11 devices operate in a differentradio frequency band than the Bluetooth system.

[0034] The key of the invention is to introduce an interoperabilitydevice in a communication system which integrates an IEEE 802.11transceiver and a Bluetooth transceiver. The device prevents that onetransceiver from transmitting while the other is receiving, which wouldcause interference at the receiving transceiver. In addition, the deviceprevents that both systems from transmitting at the same time to avoidinterference at the receiving device(s), optionally the device prohibitssimultaneous reception of both transceivers. In that way the radioreceiver can be shared between the devices, allowing a cheaper andsmaller hardware design. The invention also covers a dual band mode inwhich the IEE802.11 device and the Bluetooth device work in a differentfrequency band, and allows completely parallel operation of the twodevices.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The invention will now be described by way of example withreference to the accompanying Figures, in which:

[0036]FIG. 1 illustrates a high-level architecture for implementing thepresent invention;

[0037]FIG. 2 illustrates the architecture of FIG. 1 adapted to utiliseradio re-use in accordance with a preferred embodiment of the invention;

[0038]FIG. 3 illustrates a Bluetooth HV-i packet;

[0039]FIG. 4 illustrates the time-slot allocation for transmission ofthree different HV-i schemes;

[0040]FIG. 5 illustrates a forward and reverse packet structure for IEEE802.11; and

[0041]FIG. 6 illustrates a possible single chip implementation of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0042] The invention serves to solve a fundamental problem associatedwith providing both a Bluetooth radio system and an IEEE 802.11 radiosystem in a single device. The fundamental problem that has beenidentified is that if either one of the radio systems is transmitting,there is need to prevent the other radio system from receiving or elsethe receiving system will be drowned out by the transmitting system. Aswill be further discussed hereinbelow, further problems associated withthe dual operation of a IEEE 802.11 and Bluetooth radio system areovercome by preferred embodiments of the present invention as discussedhereinbelow.

[0043] Referring to FIG. 1, there is illustrated a high-levelarchitecture of the combination of an IEEE 802.11 radio systemtransceiver and a Bluetooth radio system transceiver in a single system,in conjunction with an interoperability device in accordance with thepresent invention. It will be understood by one skilled in the art thatonly those elements necessary for the implementation of the presentinvention are shown in FIG. 1.

[0044] The dual mode transceiver of FIG. 1 comprises: an IEEE 802.11physical layer functional element 112; an IEEE 802.11 MAC layerfunctional element 108; a Bluetooth physical layer functional element114; a Bluetooth baseband control functional element 110; and aninteroperability device 106, all of which comprise a combined IEEE802.11/Bluetooth transceiver generally designated by reference numeral100. In addition an IEEE 802.11 driver 102 and a Bluetooth driver 104are shown in FIG. 1.

[0045] The IEEE 802.11 driver 102 receives IEEE 802.11 packets from thedual mode transceiver 100 on lines 116, and transmits IEEE 802.11packets to the dual mode transceiver 100 on lines 116. The Bluetoothdriver 104 receives Bluetooth packets from the dual mode transceiver 100on lines 118, and transmits Bluetooth packets to the dual modetransceiver on lines 118. The operation of the respective drivers 102and 104 is exactly the same as their operation would be if the devicewere provided with a single IEEE 802.11 or Bluetooth transceiverrespectively. However their function may be extended in the sense thatthey pass on switching signal from application(s) to theinteroperability device 106.

[0046] The IEEE 802.11 MAC functional element 108 and the IEEE 802.11physical functional element 112 form the IEEE 802.11 transceiver of thedual mode transceiver. The IEEE 802.11 MAC functional element 108operates in accordance with the IEEE standard arrangement to controlaccess to the IEEE 802.11 transmission medium by the device to which itis connected. The IEEE 802.11 MAC functional element 108 receives andtransmits IEEE 802.11 packets to and from the interoperability device106 via lines 120, and transmits and receives IEEE 802.11 packets to andfrom the IEEE 802.11 physical layer functional element 112 via lines124. The IEEE 802.11 physical layer functional element 112 operates inaccordance with the IEEE standard arrangement to perform modulation etc.of the IEEE 802.11 packets and transmit/receive the packets via lines128, which interface the element to the device antenna.

[0047] The Bluetooth baseband control functional element 110 and theBluetooth physical layer functional element 114 form the Bluetoothtransceiver of the dual mode transceiver. The Bluetooth baseband controlfunctional element 110 operates in accordance with the Bluetoothstandard arrangement to control access to the transmission medium by thedevice to which it is connected. The Bluetooth baseband controlfunctional element 110 receives and transmits Bluetooth packets to andfrom the interoperability device 106 via lines 122, and transmits andreceives Bluetooth packets to and from the Bluetooth physical layerfunctional element 114 via lines 126. The IEEE 802.11 physical layerfunctional element 114 operates in accordance with the Bluetoothstandard arrangement to perform modulation etc. of the Bluetooth packetsand transmit/receive the packets via lines 130, which interface theelement to the device antenna.

[0048] The control of IEEE 802.11 packets and Bluetooth packets from therespective drivers 102 and 104 to the respective transceiver elements108/112 and 110/114 is controlled in accordance with the invention bythe interoperability device 106. As shown in FIG. 1, theinteroperability device is additionally connected to control circuitrywithin the device via control signal lines 132.

[0049] The dual mode transceiver 100 operates in accordance with theinvention in one of two modes. A first mode is a switching mode and asecond mode is a multiplexing mode, both of which modes are discussed infurther detail herein below.

[0050] In the switching mode of operation, the interoperability device106 deactivates the Bluetooth transceiver (110/114) whenever the IEEE802.11 transceiver (108/112) is activated, and vice versa. Theinteroperability device 106 is adapted to make the decision as to whichmode of operation to switch to or activate. There are severalalternative criteria on which the interoperability device may make thisdecision.

[0051] In a first alternative, the user of the device may decide whichmode to switch to. For instance when the user is at home and wants toconnect to the Internet through a telephone, the user may decide toswitch to Bluetooth mode and dial up to an Internet Service Provider(ISP). When the user is in the office, where an IEEE 802.11 wireless LANis present, the IEEE 802.11 mode may be selected by the user, to enablethe user to log on to the network. This mode requires the user to knowwhich is the appropriate interface to use for the chosen application.The user command will most likely be provided through an interface, suchas a screen and keypad, on the device itself, and notified to theinteroperability device 106 via a command signal from a centralprocessor or controller in the device. In addition mixed environments,where both Bluetooth and IEEE 802.11 exist, may be present for examplein an office environment.

[0052] In an alternative, the notification of the mode of operation maybe provided to the transceivers via control from the CPU through regulardrivers, or through a dedicated interoperability device driver.

[0053] In a second alternative, application software may control whichmode the device switches to. For instance when the user chooses tosynchronise a Personal Digital Assistant (PDA), the data-synchronisationapplication in the PC may tell the interoperability device to switch toBluetooth mode. When the user chooses to surf the World Wide Web (WWW),the browser application (or the network driver software supporting it)may tell the interoperability device to switch to IEEE 802.11 mode.Again, the interoperability device 106 may be instructed via a commandsignal from a central processor or controller.

[0054] In a third alternative, a protocol sniffer may determine whetherit detects the presence of an IEEE 802.11 device or a Bluetooth deviceon the air interface, and set the mode of the interoperability deviceaccordingly. When the protocol sniffer detects both Bluetooth and IEEE802.11 devices, it may choose a mode that the user has indicated aspreferential, or it may consult the user as in the first alternative.Alternatively, the protocol sniffer may let the application decide as inthe second alternative.

[0055] Thus in the switching mode the interoperability device operatesmerely to deactivate, or switch off, one of the two transceivers withinthe dual mode transceiver. This operation is transparent to thefunctional elements of the respective transceivers, and also to theother processing functionality in the device itself. When theinteroperability device is switched to “IEEE 802.11” mode thetransceiver 100 behaves as an IEEE 802.11 transceiver. When theinteroperability device is switched to “Bluetooth” mode the transceiver100 behaves as an Bluetooth transceiver.

[0056] In the switching mode, turning off one transceiver when the otheris transmitting means that the one transceiver cannot receive ortransmit when the other is transmitting. Thus when employing theswitching mode only one radio system needs to be operating at a giventime, which means that the radio hardware can be reused.

[0057]FIG. 2 illustrates the dual mode transceiver of FIG. 1re-configured to utilise radio re-use. As can be seen from FIG. 2, thefunctionality of the IEEE 802.11 physical layer functional element 112and the Bluetooth physical layer functional element 114 are combinedinto a single functional element referred to as the IEEE802.11/Bluetooth dual physical layer functional element, and denoted byreference numeral 200. The dual functional element 200 transmits andreceives IEEE 802.11 and Bluetooth packets on signal lines 204 to thedevice antenna.

[0058] The IEEE 802.11/Bluetooth dual physical layer functional elementis controlled by the interoperability device via signal lines 202 tooperate as the physical layer functional element for either IEEE 802.11or Bluetooth in accordance with the current mode of operation selected.

[0059] In the multiplexing mode of operation the IEEE 802.11 transmitteris switched off when the Bluetooth transmitter is receiving data and theBluetooth transmitter is switched off when the IEEE 802.11 device isreceiving data. In this way one radio system is never transmitting whenthe other is receiving, and vice versa. The interoperability device 106observes the rules of the medium access control protocols, and while thetransmission and reception of the IEEE 802.11 and Bluetooth radiosystems are time multiplexed, it will appear to the user that the twosystems operate in parallel. There will, however, be some performanceimpact (reduced data throughput, increased data error rate, reducedvoice quality).

[0060] Furthermore, the interoperability device 106 additionallypreferably does not allow the IEEE 802.1 and Bluetooth radio systems totransmit at the same time. Thus interference of one signal with theother at an external (remote) receiver is prevented.

[0061] In a preferred implementation of the multiplexing mode, if anIEEE 802.11 packet must be transmitted, all Bluetooth data connectionsare placed in the so-called PARK mode. The interoperability device 106will issue one HLC_Park_Mode primitive per active ACL (AsynchronousConnectionless data) connection to the Bluetooth transceiver, to put allACL connections in PARK mode. The PARK mode of the Bluetooth radiosystem will be familiar to one skilled in the art. In this way, theBluetooth radio system is deactivated whilst an IEEE 802.11 transmissiontakes place.

[0062] Although the example implementation is presented herein withreference to a discussion of the Bluetooth PARK mode, it will beappreciated by one skilled in the art that the Bluetooth HOLD mode mayalternatively be utilised.

[0063] If there are active Bluetooth SCO (Synchronous,connection-oriented voice) connections, which transmit and receiveperiodically in a 0.625 ms Bluetooth slot, then the IEEE 802.11transceiver must schedule its packet transmissions in-between theBluetooth packets. The Bluetooth SCO connections are real-time (voice)connections. The interoperability device 106 must take the full IEEEpacket exchange period into account, which includes an acknowledgementpacket (ACK) and (when the RTS/CTS transmission mode is used) an RTS andCTS packet.

[0064] Further hereinbelow a detailed implementation for scheduling IEEE802.11 packets in an active SCO connection is given. A ‘slot-stealing’scheme is explained and a calculation of data throughput that can beachieved given.

[0065] The IEEE 802.11 packets may need to be as short as a single slotwhen such a slot-stealing scheme is implemented, and this implies thatthe interoperability device 106 has to implement a packet fragmentationand re-assembly scheme, so that it can divide IEEE 802.11 packets inchunks that can be accommodated in the number of Bluetooth slots thatare available. The IEEE 802.11's own fragmentation mechanisms cannot beused, since these mechanisms assume that all fragments are sentconsecutively. In the detailed implementation described hereinbelow, asuitable fragmentation scheme is discussed.

[0066] In the following, an example is given for introducing the IEEE802.11 functionality into a Bluetooth radio system, to enable both radiosystems to function together in the same device. The following exampleis not limiting of the present invention, and the person skilled in theart will recognise that other possibilities exist for the implementationof such an architecture. However, as the Bluetooth specification isdominant the following is a preferred implementation.

[0067] The standard Bluetooth radio system uses Frequency Shift Keying(FSK) modulation, sending one bit of information per symbol time of 1μs. Thus the raw bit-rate is 1 Mbit/s. A packet consists of a preamble,containing a channel access code and a payload. The payload, in turn, isdivided into a header (containing packet type, destination address andsome other information fields) and a user payload field.

[0068] On the synchronous connection orientated (SCO) links, voicepackets are used. The voice packets are typically of the high-qualityvoice (HV) types HV1, HV2 or HV3. All of these packet types have a30-byte payload. The most robust packet, HV1, uses rate 1/3 ForwardError Correction (FEC). Packet type HV2 uses rate 2/3 FEC, and type HV3does not use FEC at all. The number of user bytes is 10,20 and 30 bytesrespectively for HV1, HV2 and HV3. The packet layout of an Hv-i (wherei=1,2,3) packet is shown in FIG. 3. The total duration of a HV-i voicepacket is 330 μs. Referring to FIG. 3, it can be seen that the Hv-ipacket 300 comprises a 72 bit preamble 302, an 18 bit header 304, and a240 bit (or 30 byte) payload 306.

[0069] In addition to the HV-i type packets, there also exists forBluetooth a data and voice (DV) type packet. The DV type packet offersthe same performance as HV3 (i.e. with no FEC), and carries a variableamount of data as well as voice in the same packet. However, a DV packetcarries only 10 user bytes, i.e. a third of HV3's user bytes. Theduration of the DV packet is 238 to 356 μs, depending on the amount ofdata carried.

[0070] Bluetooth packets are sent in time slots, which each have aduration of 625 μs. However packets must be less then 625 μs to allowthe radio system sufficient time to hop to another frequency betweentime slots. Examples of channel operation for HV1, HV2 and HV3connection are shown in FIG. 4, and described further hereinbelow.

[0071] FIGS. 4(a) to 4(c) illustrate timing diagrams for a singleBluetooth voice connection, based on HV1 (FIG. 4(a)), HV2 (FIG. 4(b)),or HV3 (FIG. 4(c)) packets. The shaded packets are in the forwarddirection (from Bluetooth master device to Bluetooth slave device), andthe clear packets are in the reverse direction (from Bluetooth slavedevice to Bluetooth master device). Eight time slots TS1 to TS8 areshown. As can be seen forward packets are sent in odd-numberedtime-slots and reverse packets are sent in even-numbered time-slots. Thefrequency hops, in accordance with the Bluetooth standard, on every timeslot, such that the frequencies f₁, to f₈ are hopped-to in times slotsTS1 to TS8 respectively.

[0072] All voice connection rates are specified to be 64 kbit/s. Toachieve this rate a HV1 packet must be sent every other slot, since inevery HV1 packet (1/3)×30×8=80 bits of user data are sent. (1/3) is theFEC used in HV1, and 30×8 is the number of bits in a 30 byte payload.One packet is sent every 2×0.625 ms time-slots, which is equal to 1.25milliseconds, 0.625 ms being the length of each slot. The user bit rateis thus 80/1.25 bits/ms=64 kbit/s. Since a voice link is full duplex,the other remaining alternate empty slots are required for the reverselink. This allocation of forward and reverse packets to time-slots isshown in FIG. 4(a).

[0073] HV2 packets carry twice the number of user bits as HV1 packetsand hence only one forward and one reverse packet is required for everyfour slots, as shown in FIG. 4(b).

[0074] HV3 packets carry twice the number of user bits as HV1 packetsand hence only one forward and one reverse packet is required for everysix slots, as shown in FIG. 4(c). Thus even if there were two HV3 linksactive, there would still be required only four time-slots in every sixtime-slots, leaving two time-slots in every six free.

[0075] As a DV packet, similar to a HV1 packet, carries only 10 userbytes, a DV packet must similarly be transmitted every other slot toachieve a rate of 64 kbit/s.

[0076] Hence in combination with a single HV1 or DV voice link, no IEEE802.11 data traffic can be transmitted or received without reducing thevoice quality of the transmission.

[0077] With a single HV2 link, or HV3 links, two slots are available forIEEE 802.11 traffic. With a single HV3 link, 4 slots are available forIEEE 802.11 traffic.

[0078] Working within these parameters set by the Bluetooth transmissionsystem, it is necessary to determine what IEEE 802.11 user bit rate ispossible, given the available time slots. As discussed furtherhereinbelow, this depends to a certain extent on the overhead of theIEEE802.11 packet.

[0079] IEEE 802.11 packets have either a short or a long preamble, of 96or 192 μs respectively. The IEEE 802.11 packet payload is transmitted ata rate of one byte in every symbol time with a duration of 8/11-th μs.This gives a bit rate of 11 Mbit/s. The payload contains a 24 byteheader and a 32 bit (4 byte) CRC field, which takes 28×(8/11)=20.3 μs tosend in total. A SIFS (Short Inter-frame Space) time of 10 μs aftercorrect reception of a packet, the recipient transmits anacknowledgement packet, which consists of a header of 96 or 192 μs. Thepayload contains MAC protocol control information of 14 bytes that take14×8/11=10.2 μs to transmit. FIG. 5 depicts an IEEE 802.11 packettransmission.

[0080] As shown in FIG. 6, an IEEE 802.11 forward data packet 500consists of a preamble 504, a MAC header 506 and a data field 508. Ifreceived correctly, the receiver, responds with an acknowledgementpacket 502 after a SIFS period. The latter packet consists of a preamble510 and an acknowledgement field 512 comprising MAC information.

[0081] There are thus 4 scenarios to consider: there are two possibleIEEE preamble lengths (96 and 192 μs); and there are either two or fourBluetooth “idle” periods (two and four slots).

[0082] The scenario where two Bluetooth slots are available fortransmission for IEEE transmissions having a long preamble isconsidered.

[0083] The overhead due to preambles, SIFS, and MAC overhead amounts to[2×192]+10+[(28+14)×(8/11)]=424.5 μs. Of the two idle slots, it ispermissible only to use 625+366=991 μs according to the Bluetoothspecification. This is to leave 625−366=259 μs to allow the radio systemto hop to the frequency of the next slot. Subtract 424.5 from 991, toget 566.5, which is the time left for actual data transmission at 11Mbit/s. In this time 566.5/(8/11)=779 IEEE 802.11 bytes can betransmitted. This data can be transmitted every 4 slots. Hence theeffective bit rate is equal to (8×779)/(4×625)=2.5 Mbit/s.

[0084] The scenario where four Bluetooth slots are available fortransmission for IEEE transmissions having a long preamble is nowconsidered.

[0085] If four Bluetooth slots are available, then the time for payloadtransmission is equal to payload time 625×3+366−424.5=1817. This Equatesto 1817/(8/11)=2498 IEEE 802.11 CCK bytes. The equivalent bit rate isnow (8×2498)/(6×625)=5.33 Mbit/s.

[0086] If the calculations are repeated for short IEEE 802.11 preambles,the bit rates are 3.33 Mbit/s for an HV2 connection or for two HV3connections. For a single HV3 connection the bit rate is 5.89 Mbit/s.The results are summarised in Table 1. TABLE 1 IEEE 802.11 throughputTwo Slots Four Slots Short preamble 3.33 5.89 Mbit/s Mbit/s longpreamble 2.49 5.33 Mbit/s Mbit/s

[0087] Table 1 shows IEEE 802.11 user throughputs if IEEE 802.11 packetsare transmitted in slots that are left idle by Bluetooth. If there isone HV2 connection or two HV3 connections, there are 2 idle slots totransmit. If there is one HV3 connection, there are 4 idle slots totransmit. If there is on HV1 or DV1 connection there are no idle slots.If there is no SCO connection at all, then all slots are available fortransmission, and the theoretical IEEE 802.11 maximum of 11 Mbit/s canbe achieved.

[0088] If a Bluetooth ACL packet must be transmitted, theinteroperability device 106 simply holds back IEEE 802.11 packets. Asthe ACL packets are none real time data packets, they can be held back.When a Bluetooth ACL packet is to be transmitted, an IEEE 802.11 packettransmission will not be in progress, as the ACL connection would be inPARK mode if an IEEE transmission was in progress, as discussedhereinabove.

[0089] In an alternative formulation, if a Bluetooth ACL packettransmission or reception is in progress, the IEEE 802.11 transmissionis held back until the Bluetooth transmission/reception is completed.Then the Bluetooth ACL connection is put in HOLD or PARK mode, and theIEEE802.11 transmission can be scheduled and organised around SCOtransmissions, as described above.

[0090] Optionally, the interoperability device has a further mode inwhich it will not allow the IEEE 802.11 devices and Bluetooth device toreceive in parallel. By not allowing this, only one radio will beoperating at a given time, which implies that the radio hardware can bereused. This again results in an architecture as shown in FIG. 2. Inthis mode Bluetooth SCO slots are always received. If neither theBluetooth nor the IEEE 802.11 transmitter need to transmit, the commonreceiver listens to either Bluetooth or IEEE 802.11 packets, accordingto an algorithm.

[0091] Such an algorithm may be static; for instance the receiverlistens to IEEE 802.11 in odd slots and to Bluetooth packets in evenslots. Also given the distribution of traffic between Bluetooth andIEEE802. 11, the algorithm could give preference to one over the other.

[0092] Finally, the receiver may have a dual synchronisation mode, whereit listens to the channel, detects on the fly what type of packet is inthe medium (Bluetooth or IEEE 802.11), and reports this to the receiver,which will switch to the appropriate reception mode.

[0093] Both IEEE 802.11 and Bluetooth Packets may be longer than asingle slot. In that case the receiver attempts to receive the packetuntil completion.

[0094] In a typical embodiment of the invention, the MAC controller ofthe IEE802.11 device and the baseband controller of the Bluetooth devicemay be implemented in separate, dedicated processor chips. Theinteroperability device's functionality may be implemented in anadditional chip. Alternatively, the functionality of theinteroperability device can be added to the controller chips of eitherthe Bluetooth or the IEE802.11 device. In a still further alternative,it is possible to integrate the IEEE 802.11 MAC control functions andthe Bluetooth control function in a single chip and add theinteroperability functionality to the same chip as well. Otherarrangements of chips and division of interoperability functionality arealso possible.

[0095]FIG. 6 illustrates an example of a “system on a chip”implementation of a combined IEEE 802.11 MAC controller and a BluetoothBaseband controller. The chip 600 includes a DMA (Direct Memory Access)610, an interrupt controller (Int. Ctrl) 612, timers 614, RAM (RandomAccess Memory) 616 all connected to a CPU (central processor unit) 622via an internal bus 624, which elements are all required for both theIEEE 802.11 and Bluetooth functions. An external bus (Ext. Bus) block608 is also required for both the IEEE 802.11 and Bluetooth functions,and is connected to the CPU 622 via internal bus 624 and to an externalflash memory and/or ROM via lines 626. A USB (Universal Serial Bus)block 606, connected to internal bus 624, is used to interface theBluetooth transceiver and optionally the IEEE 802.11 transceiver to ahost PC via connections 628. The (mini) PCI block 602, connected to theinternal bus 624, is used to interface between the host PC (viaconnections 628) and the IEEE 802.11 transceiver. A PCI based interfacebetween host PC and Bluetooth is not yet defined but is foreseen. TheUART block is also connected to the internal bus 624 and to the externalconnections 628.

[0096] The CPU micro-controller 622 runs firmware that implements theIEEE 802.11 MAC and Bluetooth baseband functions. A Bluetooth LinkController block 618 and an IEEE 802.11 MAC support block 620 areconnected to the CPU via the internal bus 624, and operate inconjunction with the CPU 622 to implement hardware assist functions forboth the Bluetooth and IEEE 802.11 transceivers respectively.

[0097] The Bluetooth Link Controller 618 is connected to the Bluetoothphysical layer functional elements (not shown) via connections 632, andsimilarly the IEEE 802.1 MAC support block 620 is connected to the IEEE802.11 physical layer functional elements (not shown) via connections634.

1. A device incorporating a first radio system operating at a firstrange of frequencies of operation and a second radio system operating ata second range of frequencies of operation, wherein at least a part ofsaid first and second range of frequencies overlap, wherein the devicefurther comprises a control means adapted to control the first andsecond radio systems such that such that only one or the other radiosystem may transmit at any one time.
 2. The device of claim 1 , whereinthe first radio system is a Bluetooth system and the second radio systemis an IEEE 802.11 system.
 3. The device of claim 1 , wherein the deviceis additionally controlled such that when one device is transmitting theother device cannot receive or transmit.
 4. The device of claim 3wherein the device is additionally controlled such that when one deviceis receiving the other device cannot receive or transmit.
 5. The deviceof claim 2 , wherein the control means comprises a switching meansadapted to switch on and off the first and second radio systems.
 6. Thedevice of claim 2 , wherein the control means comprises a multiplexingmeans adapted to time multiplex transmissions from the first and secondradio systems.
 7. The device of claim 2 , wherein the control meanscomprises a multiplexing means adapted to time multiplex transmissionsfrom the Bluetooth and IEEE 802.11 radio systems, the IEEE 802.11 andBluetooth transmissions being multiplexed into Bluetooth time-slots. 8.The device of claim 7 , wherein the Bluetooth transmissions are througha single HV2 SCO link connection, the IEEE 802.11 transmissions being intwo time-slots in every four.
 9. The device of claim 7 , wherein theBluetooth transmissions are through a single HV3 SCO link connection,the IEEE 802.11 transmissions being in four time-slots in every six. 10.The device of claim 7 , wherein the Bluetooth transmissions are throughtwo HV3 SCO link connections, the IEEE 802.11 transmissions being in twotime-slots in every six.
 11. The device of claim 2 , wherein the controlmeans prevents transmission of IEEE 802.11 packets during a BluetoothACL packet transmission.
 12. The device of claim 2 , wherein the controlmeans prevents transmission of Bluetooth ACL packets during an IEEE802.11 packet transmission.
 13. The device of claim 12 in which thefirst and second radio systems share a common physical layer.
 14. Amethod of incorporating a first radio system operating at a first rangeof frequencies of operation and a second radio system operating at asecond range of frequencies of operation, wherein at least a part ofsaid first and second range of frequencies overlap, into a singledevice, wherein the first and second radio systems are controlled suchthat only one or the other radio system transmits at any one time. 15.The method of claim 14 , wherein the first radio system is a Bluetoothsystem and the second radio system is an IEEE 802.11 system.
 16. Themethod of claim 15 further comprising controlling the radio systems suchthat when one radio system is transmitting the other cannot receive ortransmit.
 17. The method of claim 16 further comprising controlling theradio systems such that when one is receiving the other cannot receiveor transmit.
 18. The method of claim 15 , wherein the radio systems arecontrolled by switching on and off the first and second radio systems.19. The method of claim 15 , comprising time multiplexing transmissionsfrom the Bluetooth and IEEE 802.11 radio systems, the IEEE 802.11 andBluetooth transmissions being multiplexed into Bluetooth time-slots. 20.The method of claim 19 , wherein the Bluetooth transmissions are througha single HV2 SCO link connection, the IEEE 802.11 transmissions being intwo time-slots in every four.
 21. The method of claim 19 , wherein theBluetooth transmissions are through a single HV3 SCO link connection,the IEEE 802.11 transmissions being in four time-slots in every six. 22.The method of claim 19 , wherein the Bluetooth transmissions are throughtwo HV3 SCO link connections, the IEEE 802.11 transmissions being in twotime-slots in every six.
 23. The method of claim 15 further comprisingpreventing transmission of IEEE 802.11 packets during a Bluetooth ACLpacket transmission.
 24. The method of claim 15 further comprisingpreventing transmission of Bluetooth ACL packets during an IEEE 802.11packet transmission.
 25. The method of claim 24 in which the first andsecond radio systems share a common physical layer.